protected关键字对父子成员变量的影响

 include<iostream>
 #include<string>
 using namespace std;
 class parent{
 protected:
         int mv;
 public:
         parent(){
                 mv = ;
         }
         int value(){
                 return mv;
         }
 };
 class child:public parent{
 public:
         int addvalue(int v){
                 mv = mv + v;
         }
         int changemv(int v){
                 mv = v;
         }
 };
 int main(){
         parent p;
         child c;
         cout << "c.value()=" << c.value() << endl;//
         cout << "p.value()=" << p.value() << endl;//
         c.addvalue();
        cout << "c.value()=" << c.value() << endl;//
         cout << "p.value()=" << p.value() << endl;//
         cout << "c.changemv()后" << endl;
         c.changemv();
         cout << "c.mv=" << c.value() << endl;//
         cout << "p.mv=" << p.value() << endl;//
         return ;
         }

运行结果：

c.value()=100
p.value()=100
c.value()=350
p.value()=100
c.changemv()后
c.mv=380
p.mv=100

结论：

对于具有继承关系的类，父类和子类各自有各自的成员变量，子类对其成员变量的修改并不会影响父类的